COSMOS

2D Organic Semiconductor.

How Safe is your Nano?

Polymer Semiconductors Become Sophisticated.

Assembling Nanoparticles Like Making Molecules.

Associate Professor TEO Yik Ying – For his research on the genetics and genomics of complex human traits, common diseases and infectious diseases.

Assistant Professor Andrivo RUSYDI – For his research on strongly correlated electron systems and the development of synchrotron-based experimental techniques.

Assistant Professor WU Jishan – For his research on organic optoelectronic materials and supramolecular chemistry.

The pace of growth for research in Singapore is nothing short of spectacular. Though still in its infancy compared to the might of research giants like Finland, Norway, Israel, Japan, USA, UK and China, Singapore is rapidly moving into higher gear. This comes at a time when the research and development (R&D) of some of the world's leading nations has stalled due in part to the financial meltdown that has only recently seen signs of recovery.

But as the saying goes, the best opportunities are found in times of adversity. The approach that Singapore takes is an astute one. Investment in R&D for a country with no natural resources has to be based on the next best thing — intellectual capital and its people. Developing R&D capabilities in a knowledge-based economy therefore depends first and foremost on our human capital. An integrated effort in education and research is hence crucial.

The government has taken the lead in R&D investment. It has set a national target of driving the current level of 2.9% of gross domestic expenditure on research and development (GERD) to 3.5% by 2015 — a significant milestone that would put Singapore in the "premier league" of R&D nations. It is with this objective that the new national R&D budget for the next five years will be increased by more than 20% to S$16.1 billion. This increase is justified on the basis of pushing a research agenda that is driven by innovation with an economic mission.

In this review, we systematically analyzed the complicated interrelationship between photoluminescent quantum dots (QDs) and reactive oxygen species of biological importance. QDs, when photoexcited, generate reactive oxygen species (ROS), which are partially blamed for the cytotoxicity of QDs. On the positive side, the ability of generating ROS by QDs are exploited in photodynamic therapy using QDs alone or in combination with QD-surface bound organic sensitizers via resonance energy transfer from QDs to the organic dyes. Lastly, depending on the chemical composition and the functionalization of the QDs, ROS are known to quench or switch-on the QD photoluminescence. The selectivity and sensitivity toward specific ROS can be achieved through judicious chemical modification of QD surface coating layers by taking into account the reactivity difference among different ROS. The flexible QD surface functionalization opens up the unprecedented possibility of designer-made nanoprobes for sensing and quantifying ROS of biological importance.

Graphene, a single layer of hexagonal packed carbon atoms, has attracted increasing attention in recent years. Because of its exceptional electronic, optical, mechanical, and thermal properties, graphene has shown great promises in a wide range of applications. Graphene derivatives, e.g. graphene oxide (GO) and reduced graphene oxide (rGO) sheets, possess surface defects and oxygen functional groups, which make them ideal templates for synthesis of metal and semiconductor nanoparticles (NPs). Enhanced properties are expected in these graphene–NP composites, which arise from the synergic effect of the GO/rGO sheets and the anchored NPs. In this review, after a brief introduction on the properties and synthesis of graphene, we will discuss the fabrication methods of graphene–metal NP and graphene–semiconductor NP composites, as well as their related applications in catalysis, photovoltaic devices, supercapacitors, and so on.

Noble metal nanoparticles exhibit strong surface plasmon resonance (SPR) and have been utilized in many chemical, biological and electronic applications. Recent advances on metal-enhanced optical properties demonstrated that the quantum yield and photo-stability of the fluorophores can be significantly enhanced when they are in the proximity of the metal surface, that will benefit many fluorescence-based applications. In this review article we first discuss the fundamental concepts of metal-enhanced optical properties and the recent achievements of metal-enhanced fluorescence of organic fluorophores and quantum dots, as well as metal-enhanced phosphorescence of organic molecules and upconversion nanoparticles that have long life times. Finally, we present recent applications of metal-enhanced optical properties in biosensing and bioassays, photodynamic therapy and optoelectronics.

Reported was a novel amperometric immunosensor based on layer-by-layer (LbL) assembled polyethylenimine/gold nanoparticles/poly (acrylic acid) (PEI/AuNPs/PAA) multilayer. The assembly process was in situ monitored by surface plasmon resonance (SPR) technique. Anti-goat IgG as a capture antibody was covalently immobilized on the outermost PAA layer of the multilayer to construct an immunosensor. A target protein, goat IgG was electrochemically detected with alkaline phosphatase-conjugated anti-goat IgG (ALP-anti-goat IgG) as a recognition antibody. Electrochemical investigations suggest that the incorporation of AuNPs facilitates the electron transfer between the underlying electrode and the redox species in solution, and thus enhances the electrochemical signals and in turn improves the immunosensing performance. A detection limit of 100 pg mL^-1 with a dynamic range of five orders of magnitude was achieved. Due to the protein-friendly environment and the protein resistance of the polyelectrolyte multilayer, the resulting immunosensor demonstrates excellent storage stability, satisfying assay specificity.

Development of rapid, field-portable and cost-effective sensors with high sensitivity and selectivity is of great importance for biomedical diagnostics, food safety and environmental monitoring. Silica nanoparticles (SiNPs) have great potential in sensor application due to their biocompatibility, controllable surface modification, excellent chemical stability and high specific surface area. On the other hand, conjugated polyelectrolytes (CPEs) have been widely used in sensor design due to their efficient Förster resonance energy transfer (FRET) to dyes and unique interaction with biomolecules. In this contribution, we briefly summarize the recent development of silica-related NP-based assays that incorporate CPEs as the signal amplifier or reporter. The silica-related NPs are used for probe immobilization, target recognition and separation, while CPEs provide amplified fluorescence signals and high sensitivity. These assays have been proven efficient for the detection of DNA, proteins, and small molecules through specific biorecognition events, such as DNA hybridization, antibody–antigen recognition and target–aptamer binding.

In this short review, we report the facile fabrication of various interesting multi-component nanostructures including arrays of core-shell nanowires, multiwall nanotubes, segmented nanowires and multilayer stacked nanodisks, using anodized alumina membrane (AAM). We demonstrate that metallic (Cu, Ni and Au) and polymeric (PPV and PPy) one-dimensional (1D) arrays can be readily prepared by electrochemical deposition into the AAM. By optimizing the experimental design and conditions, we developed techniques to produce various multi-component nanostructures such as polymer/metal or metal/metal core-shell nanowires as well as nanotubes, with reasonably good control over both the length and the shell thickness of the nanostructures. Furthermore, we extend this method to make segmented nanowires as well as multilayer stacked nanodisks. Selective functionalization of the segmented nanowires resulted in end-on or side-on adhesion of nanowires during assembly. We illustrate the possibility of utilizing these 1D arrays to present patterns with luminescent and/or magnetic properties at this length scale.

Significant efforts in the field of colloidal semiconductor particles have been dedicated to the fabrication and study of hybrid metal–semiconductor nanoheterostructures, where the incorporation of the metal moiety may potentially enhance and/or expand existing applications of semiconductor nanoparticles. Many of these metal–semiconductor nanostructured constructs exhibit physical properties not found in either of their metal or semiconductor components, providing many opportunities for further investigation into interface and coupling effects between the two materials. We review some of the key research endeavors in this area, focusing mainly on the synthesis of the materials and the characterization of the various metal–semiconductor constructs, and highlighting some of the unique applications that have emerged from these efforts.